Answer: 2.25
Divide the corresponding values. You'll divide figure 2's length over figure 1's corresponding length. So 18/8 = 2.25
This means each side of figure 2 is 2.25 times larger than the corresponding side for figure 1
The three points give you three equations, which you can solve by your favorite method.
.. 0m +0n +b = 6
.. 1m +0n +b = -3
.. 0m +2n +b = 5
(m, n, b) = (-9, -1/2, 6)
so the equation of the plane can be written as
.. z = -9x -1/2y +6
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In standard form, this would be
.. 18x +y +2z = 12
g(x) = -3x² - 2x + 3
g(-2) = -3(-2)² - 2(-2) + 3
g(-2) = -12 + 4 + 3 = -5